A Nuclear Atom

Question 1

who was the first person who essentially discovered the basic model for the atom

Answer 1

john dalton

Question 2

what did dalton state about the atom

Answer 2

• it was simply a hard solid sphere

- that was indestructible / couldnt be further broken down

Question 3

what model did thompson come up with for the atom

Answer 3

the plum pudding model

Question 4

what did he discover about the atom for him to come up with the model

Answer 4

• that there are negatively charged electrons that could be removed from an atom
• leaving a spread out positively charged ion

Question 5

what was the plum pudding model like

Answer 5

• a positively charged sphere (the dough)

- with the negatively charged electrons scattered within it (the plums)

Question 6

who was the first person to come up with the nuclear model of the atom

Answer 6

rutherford

Question 7

what did his model state

Answer 7

• that there was a tiny charged nucleus at the centre
• which had a concentrated positive charge
• surrounded at some distance by electrons

Question 8

what experiment did rutherford carry out to come up with this model and what did it consist of

Answer 8

• the alpha particle scattering experiment
• he shot alpha particles at a thin sheet of gold
• and detected where the alpha particle emerged with detectors surrounding the sheet

Question 9

what observation of this experiment caused him to think that there was a strong concentrated positive charge

Answer 9

• some of the alpha particles were being deflected over 90 degrees
• some of those being directly back at him
• suggesting there strong electrostatic repulsion between the particle and something in the atom

Question 10

what observation caused him to think that most of an atom was empty space

Answer 10

• most of the alpha particles passed straight through without being deflected or barely being deflected
• suggesting that most of the gold sheet consisted of empty space

Question 11

what did both of those conclusions lead rutherford to suggest

Answer 11

• that there was a tiny nucleus with a strong, concentrated +ve charge
• with its electrons surrounding it being a good distance away from it (relative it their size)

Question 12

who was the person who further refined rutherford’s nuclear model of the atom

Answer 12

niel bohr

Question 13

what did he discover about the atom

Answer 13

• that electrons exist in fixed orbits (certain well defined energy levels)
• and that they could quantum leap from one energy level to the other
• if they absorbed / emitted the right amount of energy at once

Question 14

what was this theory / model of the atom called

Answer 14

the quantum theory / model

Question 15

what did chadwick discover

Answer 15

the neutron

Question 16

what are protons and neutrons in a nucleus collectively called

Answer 16

nucleons

Question 17

past an atomic number of 20, what does the relationship between the number of protons and neutrons need to be in order for the atom to remain stable

Answer 17

there generally needs to be more neutrons than protons in the nucleus

Question 18

what are the 2 reasons for there to be more neutrons than protons in order for it to remain stable

Answer 18

• the neutrons help bind the nucleus together as they exert a strong electrostatic force on other nucleons
• they also act as a space buffer between the mutually repelling positive charges of the protons within a nucleus

Question 19

how does the ratio of neutrons to protons change as the number of protons increases

Answer 19

• there will be an increasing amount of neutrons per increase of protons
• similar to a y = x^2 relationship

Question 20

although the quantum model of the atom is pretty accurate, why is the solar system-like model of the orbiting electrons practically wrong

Answer 20

because you cant know the position and velocity of an electron at the same time

Question 21

what is that idea called

Answer 21

the uncertainty principle

Question 22

what was the new model that was created in order to take this into account

Answer 22

• instead of specific orbits, atoms had regions of space around them called probability clouds
• these were regions where there was a high probability (90%) of finding an electron in them

Question 23

thinking back to chemistry, what are these probability clouds called

Answer 23

orbitals